The task group (TG) for quality assurance for robotic radiosurgery was formed by the American Association of Physicists in Medicine's Science Council under the direction of the Radiation Therapy Committee and the Quality Assurance (QA) Subcommittee. The task group (TG-135) had three main charges: (1) To make recommendations on a code of practice for Robotic Radiosurgery QA; (2) To make recommendations on quality assurance and dosimetric verification techniques, especially in regard to real-time respiratory motion tracking software; (3) To make recommendations on issues which require further research and development. This report provides a general functional overview of the only clinically implemented robotic radiosurgery device, the CyberKnife V R . This report includes sections on device components and their individual component QA recommendations, followed by a section on the QA requirements for integrated systems. Examples of checklists for daily, monthly, annual, and upgrade QA are given as guidance for medical physicists. Areas in which QA procedures are still under development are discussed.

No abstract

Purpose: The 6MV X‐band robot mounted linac in a CyberKnife(CK) system is more compact and maneuverable than conventional S‐band linacs. Long term mechanical and radiation output stability of this linac is crucial for the sub‐millimeter accuracy needed for stereotactic radiosurgery (SRS). The versatility of the CK allows for both extracranial and intracranial SRS use. The synchrony system tracks patient breathing thereby enabling precise irradiation of moving tumors. We evaluate the mechanical and radiation stability of the CK and the targeting error of synchrony with respect to variations in simulated anterior‐posterior(AP) motion using a ball‐cube phantom inside which gafchromic film is orthogonally positioned. Methods and Materials: CK output is monitored by a vented chamber unlike a sealed chamber used in conventional linacs. A daily calibration factor(CF) is obtained to correct for the changes in temperature, pressure and output. Absolute output, flatness, symmetry penumbra, End‐to‐End and Iso‐post tests are done monthly to verify the accuracy of the dose distribution and alignment of the X‐ray tube and detectors respectively. A 2D motion platform was fabricated to simulate respiration. The amplitude of motion ranged between 1cm and 3cm, a dose of 3000cGy from a 3 path fiducially tracked plan were given to the phantom at the 62% iso‐dose line The films were analyzed using End‐to‐End software and the total targeting error in the AP direction was determined. Results: Over two years of clinical use the linac output variation decreased steadily from 2% to below 1% while flatness, symmetry, and penumbra were well within CK specifications. The averaged CF was 1.011±0.008MU/cGy, the static targeting error was 0.8 ± 0.047mm and the synchrony targeting error was 1.63±0.056mm. Conclusion: We conclude that the CK mechanical system delivers the required targeting accuracy in both synchrony and static treatments, while the radiation instability is less than 2 %.

History: TG‐135 was approved by AAPM at the 2006 Annual Meeting. The intent of this TG was to fill the gap between TG‐40, which does not cover certain QA aspects of newer radiation delivery devices, and TG‐100, which will revise our current QA paradigm. General Outline of Report: The report consists of three major sections: (1) QA for individual system components, (2) QA for the integrated systems, (3) a summary with QA checklists. At the time of publication there is only one FDA‐approved robotic radiosurgery system (Cyberknife, Accuray Inc, Sunnyvale, CA) on the market, therefore the report is often vendor‐specific. Technologies which became available in the clinic after the report was submitted for review (e.g. IRIS collimator, XSight lung tracking) were not included. Major Highlights: Each individual Cyberknife component will be discussed, with reference to applicable AAPM reports and additional QA recommendations if necessary. We also highlight areas in which a good QA approach has not yet been developed. Those include the QA of the imager systems, but also periodic QA of individual beam pointing accuracy. The second section, QA for integrated systems, explains how the various subsystems interact, and how to design a QA program for the feedback loops. Similar to the individual component QA, there are areas in the integrated systems QA where more work needs to be done. This includes e.g. QA of the interaction between image quality and tracking algorithm accuracy, and individual beam pointing QA for non‐isocentric plans. The Task Groupˈs recommendations on patient‐like and individual patient QA are also included. The report summarizes daily, monthly, annual and special considerations (software and hardware upgrades, earthquakes, etc). Report as it relates to TG‐100: This report is intended to give QA recommendations based on the philosophy of TG‐40. The QM approach to robotic radiosurgery will have to be adapted to the TG‐100 philosophy after its publication, which includes the data collection for a FMEA analysis for this relatively new technology. Implementation Plan: The recommendations of TG‐135 should be critically evaluated by the site physicist after the report is published. Changes to the existing QA program should be made at the next scheduled incidence (i.e. changes for the annual QA at the next annual QA). Robotic radiosurgery is a fast‐evolving field, therefore keeping informed through reading peer‐reviewed literature and attending CE programs on QA is essential. Timeline for Report Release: TG 135 will be published in the May 2011 edition of Medical Physics. Learning Objectives: 1. Be aware of the estimated publication date for the report, report structure, and implementation plan. 2. Understand the difference between individual component QA and integrated systems QA. 3. Know which areas of robotic radiosurgery QA are still under development. 4. Anticipate the future change of QA philosophy for robotic radiosurgery with TG‐100.

History: TG‐135 was approved by AAPM at the 2006 Annual Meeting. The intent of this TG was to fill the gap between TG‐40, which does not cover certain QA aspects of newer radiation delivery devices, and TG‐100, which will revise our current QA paradigm. General Outline of Report: The report consists of three major sections: (1) QA for individual system components, (2) QA for the integrated systems, (3) a summary with QA checklists. At the time of publication there is only one FDA‐approved robotic radiosurgery system (Cyberknife, Accuray Inc, Sunnyvale, CA) on the market, therefore the report is often vendor‐specific. Technologies which became available in the clinic after the report was submitted for review (e.g. IRIS collimator, XSight lung tracking) were not included. Major Highlights: Each individual Cyberknife component will be discussed, with reference to applicable AAPM reports and additional QA recommendations if necessary. We also highlight areas in which a good QA approach has not yet been developed. Those include the QA of the imager systems, but also periodic QA of individual beam pointing accuracy. The second section, QA for integrated systems, explains how the various subsystems interact, and how to design a QA program for the feedback loops. Similar to the individual component QA, there are areas in the integrated systems QA where more work needs to be done. This includes e.g. QA of the interaction between image quality and tracking algorithm accuracy, and individual beam pointing QA for non‐isocentric plans. The Task Group's recommendations on patient‐like and individual patient QA are also included. The report summarizes daily, monthly, annual and special considerations (software and hardware upgrades, earthquakes, etc). Report as it relates to TG‐100: This report is intended to give QA recommendations based on the philosophy of TG‐40. The QM approach to robotic radiosurgery will have to be adapted to the TG‐100 philosophy after its publication, which includes the data collection for a FMEA analysis for this relatively new technology. Implementation Plan: The recommendations of TG‐135 should be critically evaluated by the site physicist after the report is published. Changes to the existing QA program should be made at the next scheduled incidence (i.e. changes for the annual QA at the next annual QA). Robotic radiosurgery is a fast‐evolving field, therefore keeping informed through reading peer‐reviewed literature and attending CE programs on QA is essential. Timeline for Report Release: At the time of abstract submission, TG‐135 was undergoing the second revision by the Therapy Physics Subcommittee. Learning Objectives: 1. Be aware of the estimated publication date for the report, report structure, and implementation plan. 2. Understand the difference between individual component QA and integrated systems QA. 3. Know which areas of robotic radiosurgery QA are still under development. 4. Anticipate the future change of QA philosophy for robotic radiosurgery with TG‐100.